Method and apparatus for controlling, during N-D or P-D shift, the engine output by a second throttle valve of a vehicle fitted with an automatic transmission

ABSTRACT

The present invention involves control of an increase in engine output of a vehicle fitted with an automatic transmission incorporating a torque converter, during a period from transmission selector operation from a stop range to a drive range up until a speed ratio (Nt/Ne) of engine rotational speed Ne to torque converter output shaft rotational speed Nt falls below a predetermined value. Control is effected by a method involving for example, maintaining a second control valve used for traction control fully closed. As a result of the invention, completion of the gear selecting operation can be accurately judged, and effects due to alleviation of gear selection shock and reduction in the load on components such as the differential can be reliably achieved.

TECHNICAL FIELD

The present invention relates to a method and an apparatus forcontrolling the engine output of a vehicle fitted with an automatictransmission incorporating torque converter, at the time of moving theshift position (referred to hereunder as selector operation) from a stoprange to a drive range.

BACKGROUND ART

Conventionally with vehicles fitted with an automatic transmissionincorporating a torque converter, in order to alleviate the gearselection shock and reduce the loading on components such as thedifferential during selector operation from a stop range (N or P range)to a drive range (D, 1, 2, R range) with the accelerator pedaldepressed, or when the accelerator pedal is depressed immediately afterselector operation to give a rapid take off, the engine output over thegear change period is reducingly corrected with respect to an outputcorresponding to the amount of depression of the accelerator pedal.

More specifically, when the engine-rotational speed is above apredetermined value at the time of selector operation, fuel injectionamount is reduced or the ignition timing is delayed so as to reduce theengine output. Then, when a time differential of the engine rotationalspeed changes from a negative to a positive value, that is, when therotational speed changes from reducing to increasing, it is judged thatthe gear selecting operation has been completed, and output reductioncorrection is terminated (see for example Japanese Unexamined PatentPublication No. 61-105228).

With the conventional gear selection control system, when in a stoprange with the engine speed reducing from a high speed, then if theaccelerator pedal is depressed so as to give a rapid take offimmediately after selector operation to a drive range, the followingproblems arise. That is to say, with the above situation, since as shownin FIG. 6 the engine rotational speed changes to increasing immediatelyafter depressing the accelerator pedal, this gives an erroneousjudgement that the gear change has been completed, and the outputreduction correction is cancelled. Thus, since the gear selectingoperation commences after the increase in engine rotational speed, thisgives rise to problems in that gear selection shock cannot besufficiently alleviated and load on components such as the differentialis increased.

In view of the above heretofore encountered problems, it is an object ofthe present invention to be able to sufficiently alleviate gearselection shock even with the above operation at the time of take off.

It is a further object of the present invention to be able to reduce theload on components such as the differential, thereby facilitating sizeand weight reduction of such components.

DISCLOSURE OF THE INVENTION

In order to achieve the above objectives, the method and apparatusaccording to the present invention for controlling the engine output ofa vehicle fitted with an automatic transmission comprises, a selectoroperation detection step or device for detecting a selector operationfrom a stop range to a drive range of the automatic transmission, aspeed ratio detection step or device for detecting a speed ratio of atorque converter output rotational speed with respect to inputrotational speed of the torque converter, and an engine output controlstep or device for controlling an increase in engine output from after aselector operation until a speed ratio detected by the speed ratiodetection step or device has fallen below a predetermined value.

With such a construction, selector operation is detected by means of theselector operation detection step or device. Then after the selectoroperation, there is a lag in the output rotational speed of the torqueconverter, (the rotational speed of the input side of the mechanicaltype transmission) with respect to the input rotational speed of thetorque converter (the engine rotational speed). This delay correspond tothe progress of engagement of the frictionally engaging componentsinside the mechanical type transmission connected to the output side ofthe torque converter. The speed ratio of the torque converter thusreduces in accordance with progress of the gear selecting operation.

Here, the engine output control step or device judges that the gearselecting operation has been completed when after the selectingoperation, the speed ratio of the torque converter detected by thebefore-mentioned speed ratio detection step or device falls below apredetermined value. Until that time, it controls the increase in engineoutput to be input to the automatic transmission.

As a result, completion of the gear selecting operation can be reliablyjudged, and since the increase in engine output can be continuouslycontrolled up until completion of the gear selecting operation, gearselection shock can always be alleviated.

Consequently, loadings on components such as the differential, due tothe sudden torque change can be reduced.

The engine may have an intake system incorporating a first throttlevalve connected to an accelerator operation, and a second throttle valvenot connected to the accelerator operation and normally maintained fullyopened, and the engine output control step or device may be constructedso as to control the increase in engine output by controlling the secondthrottle valve closing.

With such a construction, control of the second throttle valve closinggives good control of the increase in engine output without influencingconditions such as air-fuel ratio.

Moreover, when a second throttle valve is provided, the construction maybe such that the engine output control step or device involves graduallyreducing the closing amount of the second throttle valve after the speedratio has fallen below a predetermined value, until fully open.

In this case, even after completion of the gear selecting operation, anysudden increase of engine output can be suppressed so that the torquechange becomes smoother, with an improvement in comfortable.

Furthermore, the construction may be such that a throttle valve fortraction control which is controlled to close from fully open when wheelslip above a predetermined value occurs may be used as the secondthrottle valve. In this case, control can be effected without specialequipment, by merely adding a control program.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the structure and functions of thepresent invention.

FIG. 2 is a schematic diagram illustrating a system layout of anembodiment according to the present invention.

FIG. 3 is a schematic diagram of a hydraulic circuit for an automatictransmission of the embodiment.

FIG. 4 is a flow chart for an engine output control routine for theembodiment according to the present invention.

FIG. 5 is a time chart illustrating operating conditions according tothe embodiment.

FIG. 6 is a time chart illustrating conventional operating conditions.

BEST MODE FOR CARRYING OUT THE INVENTION

The previously mentioned method and apparatus for controlling the engineoutput of a vehicle fitted with an automatic transmission according tothe present invention comprises the various steps and devices as shownin FIG. 1. The construction and operation of an embodiment of thepresent invention are illustrated in FIG. 2 through FIG. 5.

In FIG. 2 which shows the construction of an embodiment, an automatictransmission 2 incorporating a torque converter is connected to anoutput shaft of an engine 1.

As shown in FIG. 3, the automatic transmission 2 comprises atransmission with incorporates various components such as a torqueconverter 20, a servo band 21, a reversing clutch 22, a high clutch 23,a forward clutch 24, a forward one way clutch 25, an overrunning clutch26, a low and reverse brake 27, a low one way clutch 28, and front andrear planetary gear sets 29. Solenoid valves 2A-2E (see FIG. 2) forcontrolling the operating hydraulic pressure for the various speedchange components are provided in hydraulic flow paths to thecomponents, and the operating pressure controlled by controlling thevalve open duty.

The automatic transmission 2 further incorporates a shift positionsensor 3 for detecting the various shift positions, and a turbinerotational speed sensor 4 for detecting the rotational speed NT of theoutput shaft (turbine shaft) of the torque converter 20. The outputsignals from these sensors are input to an AT (automatic transmission)control unit 5.

Control signals are output from the AT control unit 5 to the solenoidvalves which control the hydraulic pressure to the respective speedchange components of the automatic transmission 2, to thereby effect thevarious speed change controls.

A first throttle valve 6 connected to the accelerator pedal (not shownin the figure) and a second throttle valve 7 for traction control areprovided in the intake passage of the engine 1. The second throttlevalve 7 is controlled by a control signal from a traction control unit8, by way of an actuator 9 such as a stepping motor, so as to close fromfully open when wheel slip above a predetermined value occurs duringacceleration and the like. An opening sensor 10 for detecting valveopening is fitted to the second throttle valve 7.

An engine control unit 11 is also provided for controlling suchfunctions as fuel injection amount and ignition timing of the engine 1.Detection signals from the engine rotational speed sensor 12 are inputto the engine control unit 11 and the traction control unit 8.

As well as carrying out the beforementioned normal traction controlbased on wheel slip, the traction control unit 8 also controls theclosing of the second throttle valve 7 according to the presentinvention, depending on a gear selection control signal from the ATcontrol unit 5 based on the selector operation from the stop range tothe drive range of the torque converter 20 and the speed ratio of thetorque converter 20.

As follows is a description in accordance with the flow chart of FIG. 4,of the closing control of the second throttle valve 7 carried out by thetraction control unit 8 based on a gear selection control signal fromthe AT control unit 5.

In step 1, the setting condition of a flag F1 which is set at the timeof selector operation from a stop range to a drive range of theautomatic transmission 2 is judged.

If judged that flag F1 is not set to 1, control proceeds to step 2 andit is judged if a selector operation from a stop range to a drive rangehas been made. If judged to have been made, control proceeds to step 3where flag F1 is set to 1, and then proceeds to step 5. Also, at a latertime with the judgement of step 1 as YES, control proceeds to step 5.Here the selector operation detection device comprises the shiftposition sensor 3 and the judgement function of step 2.

In step 2, if judged that selector operation to the drive range has notbeen made, control proceeds to step 4 to keep the second throttle valve7 fully open and, then proceeds to step 9.

In step 5, it is judged if the speed ratio of the torque converter 20has reached a value corresponding to that at the time of completing agear selecting operation. Here the speed ratio (Nt/Ne)is obtained as theratio of the rotational speed Nt of the output shaft (turbine shaft) ofthe torque converter 20 detected by the turbine rotational speed sensor4 with respect to the engine rotational speed Ne detected by the enginerotational speed sensor 12. The speed ratio detection device thereforecomprises the engine rotational speed sensor 12, the turbine rotationalspeed sensor 4 and the function of the step 5.

Up until the speed ratio of the torque converter 20 reaches a valuecorresponding to that at the time of completing a gear selectingoperation, control proceeds to step 6, and after fully closing thesecond throttle valve (minimum opening), proceeds to step 9. Theincrease in engine output is thus controlled. The engine output controldevice thus comprises the function of step 6.

In step 5, when judged that the speed ratio of the torque converter 20has reached a value corresponding to that at the time of completing agear selecting operation, control proceeds to step 7 where flag F1 isreset to 0, from there to step 8 where flag F2 is set to 1, and then onto step 9.

In step 9, the value of flag F2 is judged. With control via step 4 andstep 6, the value of flag F2 is 0, so that control proceeds from step 9to step 11. However, when control proceeds via step 8 to step 9, it thencontinues on to step 10 where the opening of the second throttle valve 7is gradually increased. Then when fully open, the flag F2 is reset to 0and control proceeds to step 11.

In step 11, it is judged if a selector operation from a drive range to astop range of the automatic transmission 2 has been made.

If judged that a selector operation to the stop range has been made,control proceeds to step 12 to return the second throttle valve 7 tofully open. Control then proceeds to step 13 where flags F1, F2 arereset to 0, after which the routine is terminated. In step 11, if judgedthat a selector operation to the stop range has not been made, theroutine is terminated in that condition.

If such control is carried out, then as shown in FIG. 5, when the speedof the engine 1 is reducing from a high speed, then even with depressionof the accelerator pedal so as to give a rapid take off immediatelyafter a selector operation from a stop range to a drive range, bydetecting the speed ratio the second throttle valve 7 can be maintainedfully closed so as to control the increase in output from the engine 1up until completion of the gear selecting operation. Therefore, as wellas preventing excessive torque transmission force during selectoroperation and alleviating gear selection shock, the load on componentssuch as the differential is reduced, thereby facilitating size andweight reduction of such components due to reduced endurance strengthrequirements.

Furthermore, with the present embodiment, once the gear selectingoperation has been completed, the second throttle valve 7 is graduallyopened until fully open. Any sudden increase of engine output can thusbe suppressed so that the torque change becomes smoother, with animprovement in comfort.

The present embodiment is applied to a device having a second throttlevalve for carrying out traction control. However it is of course alsoapplicable to a device wherein the opening of a single throttle valve iselectronically controlled through an actuator, corresponding to anamount of depression of the accelerator pedal. In this case theconstruction may be such that during the time from immediately afterdetection of a selector operation from a stop range to a drive rangeuntil the speed ratio has fallen below a predetermined value, thethrottle valve is forcibly maintained below a predetermined opening.Throttle valve control of the increase in engine output has theadvantage that conditions such as air-fuel ratio are not influenced.However, the construction may be such that the increase in engine outputis controlled by reducing the fuel injection amount or retarding theignition timing.

As described above, the construction of the present invention involvescontrol of the increase in engine output during the period fromimmediately after selector operation from a stop range to a drive rangeof the automatic transmission until the speed ratio has fallen below apredetermined value and the gear selecting operation has been completed.Consequently, gear selection shock can be reliably alleviated and theload on components such as the differential can be reduced, enabling areduction in endurance strength requirements.

INDUSTRIAL APPLICABILITY

With the above described method and apparatus for controlling the engineoutput of a vehicle fitted with an automatic transmission according tothe present invention, since the gear selection shock in vehicles fittedwith an automatic transmission can be alleviated at the time of selectoroperation, then ride comfort can be improved together with an increasein durability of components such as the differential. The vehicle isthus given a luxurious quality, which contributes to the automotiveindustry.

The claims defining the invention are as follows:
 1. An apparatus forcontrolling an output of an engine of a vehicle fitted with an automatictransmission including a torque converter, wherein the engine has anintake system which includes a first throttle valve connected to anaccelerator operation of the vehicle, and a second throttle valve notconnected to the accelerator operation and normally maintained in afully opened state, the apparatus comprising:selector operationdetection means for detecting a selector operation from one of a neutral(n) range and a parking (p) range to a drive range of the automatictransmission; speed ratio detection means for detecting a speed ratiocorresponding to an output rotational speed of the torque converter withrespect to an input rotational speed of the torque converter; and engineoutput control means for placing and maintaining the second throttlevalve in a fully closed state from when the selector operation wasdetected until when the detected speed ratio has fallen below apredetermined value, wherein the output of the engine is controlled as aresult thereof.
 2. An apparatus for controlling an output of an engineof a vehicle fitted with an automatic transmission as claimed in claim1, wherein the engine output control means includes means for graduallyopening the second throttle valve from the fully closed state after thespeed ratio has fallen below the predetermined value until when thesecond throttle valve is in the fully open state.
 3. An apparatus forcontrolling an output of an engine of a vehicle fitted with an automatictransmission as claimed in claim 1, further comprising:means fordetermining an amount of wheel slip of the vehicle, wherein the secondthrottle valve has a traction control function which is operative to setthe second throttle valve to the fully closed state from a previouslyopen state when the amount of wheelslip becomes greater than a secondpredetermined value.
 4. An apparatus for controlling an output of anengine of a vehicle fitted with an automatic transmission as claimed inclaim 2, further comprising:means for determining an amount of wheelslip of the vehicle, wherein the second throttle valve has a tractioncontrol function which is operative to set the second throttle valve tothe fully closed state from a previously open state when the amount ofwheel slip becomes greater than a second predetermined value.
 5. Amethod for controlling an output of an engine of a vehicle fitted withan automatic transmission including a torque converter, wherein theengine has an intake system which includes a first throttle valveconnected to an accelerator operation of the vehicle, and a secondthrottle valve not connected to the accelerator operation and normallymaintained in a fully opened state, the method comprising the stepsof:a) detecting a selector operation from one of a neutral (n) range anda parking (p) range to a drive range of the automatic transmission; b)detecting a speed ratio corresponding to an output rotational speed ofthe torque converter with respect to an input rotational speed of thetorque converter; and c) placing and maintaining the second throttlevalve in a fully closed state from when the selector operation wasdetected until when the detected speed ratio has fallen below apredetermined value, wherein the output of the engine is controlled as aresult thereof.
 6. A method for controlling an output of an engine of avehicle fitted with an automatic transmission as claimed in claim 5,wherein the step c) further includes gradually opening the secondthrottle valve from the fully closed state after the speed ratio hasfallen below the predetermined value until when the second throttlevalve is in the fully open state.
 7. A method for controlling an outputof an engine of a vehicle fitted with an automatic transmission asclaimed in claim 5, further comprising the step of:d) determining anamount of wheel slip of the vehicle, wherein the second throttle valvehas a traction control function which is operative to set the secondthrottle valve to the fully closed State from a previously open statewhen the amount of wheel slip becomes greater than a secondpredetermined value.
 8. A method for controlling an output of an engineof a vehicle fitted with an automatic transmission as claimed in claim6, further comprising the step of:d) determining an amount of wheel slipof the vehicle, wherein the second throttle valve has a traction controlfunction which is operative to set the second throttle valve to thefully closed state from a previously open state when the amount of wheelslip becomes greater than a second predetermined value.